Air blower

ABSTRACT

A bottomed rotor member includes a rotor member bottom portion that forms a bottom portion of the bottomed rotor member while an opening hole is formed in the rotor member bottom portion to extend through the rotor member bottom portion in an axial direction of a fan central axis. A fan boss includes: a fan boss bottom portion that is stacked on the rotor member bottom portion in the axial direction and forms a bottom portion of the fan boss; and a bottom portion rib that projects from the fan boss bottom portion toward the rotor member bottom portion side at a corresponding location of the fan boss bottom portion that is overlapped with the opening hole in the axial direction while the bottom portion rib promotes discharge of air from the inside of the bottomed rotor member through the opening hole in response to rotation of the fan.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2015-7923 filed on Jan. 19, 2015.

TECHNICAL FIELD

The present disclosure relates to an air blower that drives a fan through an electric motor of an outer rotor type.

BACKGROUND ART

This type of air blower is disclosed in, for example, the patent literature 1. In order to introduce cooling air into an inside of the outer rotor to cool the electric motor, the air blower, which is disclosed in the patent literature 1, includes discharge outputs, which discharge the cooling air, and air-blowing projections, which generate the air flow in the inside of the outer rotor. The discharge outlets and the air-blowing projections are formed at a bottom portion of a yoke, which is shaped into a bottomed cylindrical tubular form. The air-blowing projections are respectively formed by cutting and generally perpendicularly bending a corresponding part of the bottom portion of the yoke, which forms the corresponding discharge outlet.

CITATION LIST Patent Literature

[PATENT LITERATURE 1] JP2012-110130A

SUMMARY OF THE INVENTION

However, in the air blower of the patent literature 1, in a case where each of the air-blowing projections is formed at the inside of the yoke by cutting and bending the corresponding part of the bottom portion of the yoke, which forms the corresponding discharge outlet, a size of the electric motor is disadvantageously increased in an axial direction in order to avoid an interference of the air-blowing projections to, for example, stator coils received in the inside of the outer rotor.

On the other hand, in the air blower of the patent literature 1, in another case where each of the air-blowing projections is formed at the outside of the yoke by cutting and bending the corresponding part of the bottom portion of the yoke, which forms the corresponding discharge outlet, the size of the electric motor is also disadvantageously increased in the axial direction since the air-blowing projections project from the yoke in the axial direction.

As discussed above, although the air blower of the patent literature 1 improves the cooling performance of the electric motor with the air-blowing projections, the size of the electric motor is disadvantageously increased in the axial direction. As a result of the extensive study of the inventor, the above point is found.

The present disclosure is made in view of the above point, and it is an objective of the present disclosure to provide an air blower that can improve cooling performance of an electric motor of an outer rotor type while limiting an increase in a size of the electric motor in an axial direction.

In order to achieve the above objective, according to one aspect of the present disclosure, an air blower includes: a fan that includes: a fan boss, which is shaped into a bottomed tubular form; and a plurality of blades, which are formed at an outer side of the fan boss, wherein the fan is rotatable about a fan central axis; and an electric motor that includes: an outer rotor that is placed in an inside of the fan boss and includes a bottomed rotor member, wherein the bottomed rotor member is shaped into a bottomed tubular form and is rotatable integrally with the fan boss; and a stator that is a non-rotatable member placed in an inside of the bottomed rotor member, wherein: the bottomed rotor member includes a rotor member bottom portion that forms a bottom portion of the bottomed rotor member while an opening hole is formed in the rotor member bottom portion to extend through the rotor member bottom portion in an axial direction of the fan central axis; the fan boss includes: a fan boss bottom portion that is stacked on the rotor member bottom portion in the axial direction and forms a bottom portion of the fan boss; and a bottom portion rib that projects from the fan boss bottom portion toward the rotor member bottom portion side at a corresponding location of the fan boss bottom portion that is overlapped with the opening hole in the axial direction while the bottom portion rib promotes discharge of air from the inside of the bottomed rotor member through the opening hole in response to rotation of the fan.

With the above construction, the fan boss includes the bottom portion rib that promotes the discharge of the air from the inside of the bottomed rotor member through the opening hole in response to the rotation of the fan. Furthermore, the bottom portion rib projects from the fan boss bottom portion toward the rotor member bottom portion side at the corresponding location of the fan boss bottom portion that is overlapped with the opening hole in the axial direction. Therefore, a projecting height of the bottom portion rib can be increased by using a thickness of the rotor member bottom portion. Thereby, in comparison to the structure of the air blower of the patent literature 1, in which the air-blowing projection, which corresponds to the bottom portion rib, is formed in the yoke, which corresponds to the bottomed rotor member, it is possible to improve the cooling performance of the electric motor while limiting the increase in the size of the electric motor in the axial direction.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of an air blower taken from an air intake side of the air blower according to a first embodiment.

FIG. 2 is a back view of the air blower of FIG. 1 taken from an opposite side that is opposite from the side shown in FIG. 1.

FIG. 3 is a view taken along line III-III in FIG. 1, showing an inside structure of the air blower according to the first embodiment.

FIG. 4 is a view taken in a direction of an arrow IV in FIG. 3, showing only a yoke and a fan boss, which are taken out from the air blower.

FIG. 5 is a perspective cross sectional view showing a cross section of only the yoke and the fan boss, which are taken out from the air blower, according to the first embodiment.

FIG. 6 is a view of the fan boss alone taken in the direction of the arrow IV in FIG. 3 according to the first embodiment.

FIG. 7 is a view of the fan boss alone taken in the direction of the arrow IV in FIG. 3 according to a second embodiment, corresponding to FIG. 6 of the first embodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following respective embodiments, portions, which are identical to each other or equivalent to each other, are indicated by the same reference signs in the drawings.

First Embodiment

FIG. 1 is a front view of an air blower 8 taken from an air intake side of the air blower according to the present embodiment. FIG. 2 is a back view of the air blower 8 taken from an opposite side that is opposite from the side shown in FIG. 1. The air blower 8, which is shown in FIGS. 1 and 2, is an axial blower that blows air drawn from one axial side of a fan central axis CLf (see FIG. 3), which is a rotational center of a fan 20 of the air blower 8, toward the other axial side.

FIG. 3 is a view taken along line III-III in FIG. 1, showing an inside structure of the air blower 8. As shown in FIGS. 1 and 3, the air blower 8 blows the air along the fan central axis CLf, as indicated by an arrow FLf, when the fan 20 is rotated about the fan central axis CLf in a fan rotational direction DRf.

The air blower 8 includes an electric motor 10, the fan 20, a fan shroud 30 and a drive unit 40. The electric motor 10 is an outer rotor type. The fan 20 is rotated by the electric motor 10 and generates a flow of the air. The fan shroud 30 surrounds the fan 20 and guides the air. The drive unit 40 controls energization of the electric motor 10.

The electric motor 10 includes a housing 11, a shaft 12, an outer rotor 14, and a stator 15.

The housing 11 is a non-rotatable member fixed to the fan shroud 30. The shaft 12, which is shaped into a cylindrical column form and has the fan central axis CLf as a central axis thereof, is fixed to the housing 11.

The outer rotor 14 includes a yoke 141, which is made of metal, and permanent magnets 142. The yoke 141 is a bottomed rotor member, which is shaped into a bottomed cylindrical tubular form and is made of metal. The yoke 141 is connected to the shaft 12 through a bearing and is rotatable about the fan central axis CLf relative to the shaft 12.

The yoke 141 includes a yoke bottom portion 141 a and a yoke tubular portion 141 b. The yoke bottom portion 141 a serves as a rotor member bottom portion that forms a bottom portion of the yoke 141. The yoke tubular portion 141 b is shaped into a cylindrical tubular form that has the fan central axis CLf as a central axis thereof. The yoke tubular portion 141 b is joined to the yoke bottom portion 141 a through one end 141 d of the yoke tubular portion 141 b. The permanent magnets 142 are fixed to an inner peripheral side of the yoke tubular portion 141 b.

Furthermore, as shown in FIG. 4, a plurality of opening holes 141 c extends through the yoke bottom portion 141 a in a fan axial direction that is an axial direction of the fan central axis CLf. FIG. 4 is a view taken in a direction of an arrow IV in FIG. 3, showing only a yoke and a fan boss 21 of the fan 20. The opening holes 141 c, which are formed in the yoke bottom portion 141 a, are arranged one after another at equal intervals in a fan circumferential direction, which is a circumferential direction about the fan central axis CLf. The opening holes 141 c serve as cooling holes that conduct the air for cooling the electric motor 10.

As shown in FIG. 3, the stator 15 includes coils 152 that are wound around an iron core, and the stator 15 is placed in an inside of the outer rotor 14. The stator 15 is a non-rotatable member that is fixed to the housing 11. The coils 152 of the stator 15 are energized by the drive unit 40, and a voltage of the coils 152 is controlled by the drive unit 40.

The fan 20 is an axial fan and includes the fan boss 21 and a plurality of blades 22 made of resin. The fan boss 21 is shaped into a bottomed cylindrical tubular form. The blades 22 are formed at an outer side of the fan boss 21. Specifically, as shown in FIG. 1, the blades 22 are place at an outer peripheral side of the fan boss 21 and extend radially outer side from the fan boss 21. The blades 22 are arranged one after another at equal intervals in the fan circumferential direction. The fan boss 21 and the blades 22 are integrally molded together as a one-piece body.

As shown in FIG. 3, the fan boss 21 includes a fan boss bottom portion 211 and a fan boss tubular portion 212. The fan boss bottom portion 211 forms a bottom portion of the fan boss 21. The fan boss tubular portion 212 is shaped into a cylindrical tubular form that has the fan central axis CLf as a central axis thereof. The fan boss tubular portion 212 is joined to the fan boss bottom portion 211 through one end 212 c of the fan boss tubular portion 212.

Specifically, the fan boss bottom portion 211 includes an insert member 211 a and an outer peripheral resin portion 211 b. The insert member 211 a is a metal plate. The outer peripheral resin portion 211 b is made of resin and is placed at an outer peripheral side of the insert member 211 a. The insert member 211 a and the outer peripheral resin portion 211 b are integrally formed by insert molding.

Furthermore, the fan boss tubular portion 212 is placed on a radially outer side of the yoke 141. In other words, the yoke 141 is placed at the inside of the fan boss 21. The fan boss bottom portion 211 is stacked on the yoke bottom portion 141 a in the fan axial direction and is fixed to the yoke bottom portion 141 a with, for example, screws. In this way, the outer rotor 14, which includes the yoke 141, is rotated about the fan central axis CLf integrally with the fan 20, which includes the fan boss 21.

Furthermore, as shown in FIGS. 4 and 5, the fan boss 21 includes a plurality of bottom portion ribs 213, which project from the fan boss bottom portion 211 toward the yoke bottom portion 141 a side. FIG. 5 is a perspective cross sectional view showing a cross section of only the yoke 141 and the fan boss 21. The bottom portion ribs 213 of the fan boss 21 are respectively placed at corresponding locations of the fan boss bottom portion 211 that respectively overlap with the opening holes 141 c of the yoke bottom portion 141 a. The bottom portion ribs 213 promote discharge of the air from the inside of the yoke 141 through the opening holes 141 c in response to the rotation of the fan 20. This flow of the air is indicated by a dotted arrow FLa in FIG. 3.

Specifically, as indicated by the dotted arrow FLa in FIG. 3, a portion of the air, which is fed by the blades 22, enters the inside of the yoke 141 from the side that is opposite from the yoke bottom portion 141 a side. Then, this air in the inside of the yoke 141 flows through the opening holes 141 c (see FIG. 4) and enters an axial gap between the yoke bottom portion 141 a and the fan boss bottom portion 211. Furthermore, the air, which is supplied into this axial gap, is outputted to an outside of the fan boss 21 through a radial gap that is communicated with the axial gap and is formed between the yoke tubular portion 141 b and the fan boss tubular portion 212.

Specifically, as shown in FIG. 5, each of the bottom portion ribs 213 of the fan boss 21 is formed such that at least a portion of the bottom portion rib 213 (e.g., a distal end part 213 b of the bottom portion rib 213) is inserted into the inside of the corresponding opening hole 141 c of the yoke bottom portion 141 a. Furthermore, each bottom portion rib 213 is formed such that the bottom portion rib 213 does not project from the opening hole 141 c toward the stator 15 (see FIG. 3) in the fan axial direction.

Here, the fan boss bottom portion 211 includes a rib connecting part 211 c, to which a base end 213 a of each bottom portion rib 213 is joined, at a corresponding location of the fan boss bottom portion 211 that is overlapped with the opening holes 141 c of the yoke bottom portion 141 a in the fan axial direction. The rib connecting part 211 c is spaced from the yoke bottom portion 141 a in the fan axial direction by a corresponding distance. In other words, the rib connecting part 211 c is placed such that the rib connecting part 211 c forms an axial gap between the rib connecting part 211 c and the yoke bottom portion 141 a. Therefore, a height of the bottom portion rib 213 measured from the rib connecting part 211 c is set to be equal to or smaller than a sum of a length of the axial gap discussed above and an axial thickness of the portion of the yoke bottom portion 141 a located around the opening hole 141 c.

The bottom portion ribs 213 of the fan boss 21 are arranged one after another in the fan circumferential direction, as shown in FIG. 4. Each of primary air flow passages 211 d is formed between corresponding adjacent two of the bottom portion ribs 213. The primary air flow passage 211 d extends from an inner side to an outer side in a radial direction of the fan central axis CLf. That is, the air, which is outputted from the opening hole 141 c of the yoke bottom portion 141 a to the outside of the yoke 141, is guided by the primary air flow passage 211 d toward the outer side in the radial direction of the fan central axis CLf (see FIG. 3).

As shown in FIG. 4, the fan boss tubular portion 212 of the fan boss 21 is placed on the radially outer side of the yoke tubular portion 141 b such that the radial gap discussed above is interposed between the yoke tubular portion 141 b and the fan boss tubular portion 212. The fan boss 21 includes a plurality of tubular portion ribs 214, which project from the fan boss tubular portion 212 toward an inner side of the fan boss tubular portion 212 through the radial gap described above. The tubular portion ribs 214 are outer peripheral side ribs, which are located on the radially outer side of the bottom portion ribs 213 in the inside of the fan boss 21.

Furthermore, as shown in FIGS. 5 and 6, in the inside of the fan boss 21, each of the tubular portion ribs 214 extends along the fan boss bottom portion 211 from an inner peripheral surface 212 a of the fan boss tubular portion 212 to a location of a radially outer side part of the bottom portion rib 213 in the radial direction of the fan central axis CLf. FIG. 6 is a view after removal of the yoke 141 from FIG. 4, i.e., a view of the fan boss 21 alone taken in the direction of the arrow IV in FIG. 3. In the following discussion, the radial direction of the fan central axis CLf will be also referred to as a fan radial direction.

The tubular portion ribs 214 of the fan boss 21 are arranged one after another in the fan circumferential direction. Each of secondary air flow passages 212 b is formed between corresponding adjacent two of the tubular portion ribs 214 such that the secondary air flow passage 212 b extends in the fan axial direction along the inner peripheral surface 212 a of the fan boss tubular portion 212. That is, the secondary air flow passage 212 b guides the air from the one end 212 c side of the fan boss tubular portion 212, which is the fan boss bottom portion 211 side in the fan axial direction, toward the other end 212 d side of the fan boss tubular portion 212, which is opposite from the one end 212 c in the fan axial direction. Therefore, an upstream end of the secondary air flow passage 212 b is located at the one end 212 c side of the fan boss tubular portion 212, and a downstream end of the secondary air flow passage 212 b is located at the other end 212 d side of the fan boss tubular portion 212.

Furthermore, since the tubular portion ribs 214 extend to the fan boss bottom portion 211, the upstream side of each secondary air flow passage 212 b extends to the fan boss bottom portion 211. Therefore, the primary air flow passages 211 d are formed such that as indicated by dotted hatching in FIG. 6, each primary air flow passage 211 d is continuous to corresponding one of the secondary air flow passages 212 b. In other words, the bottom portion ribs 213 are respectively formed such that the flow of the air, which is outputted from the corresponding primary air flow passage 211 d, extends continuously into the corresponding secondary air flow passage 212 b.

Specifically, as shown in FIG. 6, each of the bottom portion ribs 213 is connected to a corresponding one of the tubular portion ribs 214 at a radially outer end of the bottom portion rib 213. In this way, each of the primary air flow passages 211 d is connected in series with the corresponding one of the secondary air flow passages 212 b. The dotted hatching of FIG. 6 indicates only one of the connections, each of which connects between the corresponding primary air flow passage 211 d and the corresponding secondary air flow passage 212 b.

Furthermore, the bottom portion ribs 213 and the tubular portion ribs 214 are formed to function as fan blades of a centrifugal fan to generate the flow of the air from the radially inner side to the radially outer side in the fan radial direction in the primary and secondary air flow passages 211 d, 212 b. Specifically, the bottom portion ribs 213 are curved in a common direction in the fan circumferential direction.

In the view taken in the fan axial direction, each of the bottom portion ribs 213 and the tubular portion ribs 214 is tilted relative a corresponding fan radial direction in a manner similar to that of fan blades of a turbo fan. That is, each of the tubular portion ribs 214 is tilted relative to the corresponding fan radial direction in a counter-rotational direction that is opposite from the fan rotational direction DRf such that the amount of displacement of the tubular portion rib 214, which is measured from the corresponding fan radial direction of the fan central axis CLf in the counter-rotational direction, is progressively increased toward the radially outer side in the corresponding fan radial direction of the fan central axis CLf. Also, each of the bottom portion ribs 213 is tilted relative to the corresponding fan radial direction in the counter-rotational direction that is opposite from the fan rotational direction DRf such that the amount of displacement of the bottom portion rib 213, which is measured from the corresponding fan radial direction of the fan central axis CLf in the counter-rotational direction, is progressively increased toward the radially outer side in the corresponding fan radial direction of the fan central axis CLf.

As discussed above, the bottom portion ribs 213 and the tubular portion ribs 214 are formed in the inside of the fan boss 21 and have the function of the centrifugal fan in response to the rotation of the fan 20. Therefore, the bottom portion ribs 213 and the tubular portion ribs 214 promote the outflow of the air from the inside of the yoke 141 of the electric motor 10 (see FIG. 3) to the outside of the yoke 141 through the opening holes 141 c (see FIG. 4). That is, the bottom portion ribs 213 and the tubular portion ribs 214 promote the cooling of the electric motor 10 by the air that flows in the inside of the yoke 141.

As discussed above, according to the present embodiment, the fan boss 21 includes the bottom portion ribs 213, which promote the discharge of the air from the inside of the yoke 141 through the opening holes 141 c in response to the rotation of the fan 20. Each of the bottom portion ribs 213 projects from the fan boss bottom portion 211 toward the yoke bottom portion 141 a at the corresponding location of the fan boss bottom portion 211 where the bottom portion rib 213 is overlapped with the corresponding opening hole 141 c of the yoke bottom portion 141 a in the fan axial direction. Therefore, a projecting height of the bottom portion rib 213 can be increased by using the thickness of the yoke bottom portion 141 a. As a result, in comparison to the structure of the air blower of the patent literature 1, in which the air-blowing projections, which correspond to the bottom portion ribs 213, are formed in the yoke, it is possible to improve the cooling performance for cooling the electric motor 10 by the air that flows in the inside of the yoke 141 while limiting an increase in a size of the electric motor 10 in the fan axial direction.

Here, it should be noted that the projecting height of each bottom portion rib 213, which is formed in the inside of the fan boss 21, may be increased within an extent that does not cause an interference of the bottom portion rib 213 with the non-rotatable member, such as the stator 15 formed in the inside of the outer rotor 14 of the electric motor 10. Furthermore, it is confirmed that according to the present embodiment, when the bottom portion ribs 213 are formed, the amount of air flow, which flows between the corresponding tubular portion ribs 214, is increased by about 9% in comparison to a comparative case, in which the bottom portion ribs 213 are absent.

Furthermore, each of the bottom portion ribs 213 of the fan boss 21 is formed such that at least a portion of the bottom portion rib 213 is inserted into the inside of the corresponding opening hole 141 c of the yoke bottom portion 141 a. Therefore, in comparison to a structure, in which the bottom portion rib 213 is not inserted into the opening hole 141 c, the projecting height of the bottom portion rib 213 can be increased. Thereby, the cooling performance of the electric motor 10 can be improved. Furthermore, when the fan 20 is installed to the yoke 141, the bottom portion ribs 213 can be used for the positioning of the fan 20 relative to the yoke 141. Thereby, the assemblability of the fan 20 relative to the yoke 141 can be improved.

Furthermore, according to the present embodiment, the bottom portion ribs 213 are respectively formed such that the bottom portion rib 213 does not project from the corresponding opening hole 141 c of the yoke bottom portion 141 a toward the stator 15 side. Therefore, when the fan 20 is rotated, it is possible to limit interference between each bottom portion rib 213 and the non-rotatable member installed in the inside of the yoke 141. Furthermore, it is possible to limit an increase in the size of the electric motor 10 in the fan axial direction, which would be otherwise caused by the provision of the bottom portion ribs 213.

According to the present embodiment, the rib connecting part 211 c, which is the part of the fan boss bottom portion 211 and to which the base end 213 a of each bottom portion rib 213 is joined, is spaced from the yoke bottom portion 141 a in the fan axial direction by the corresponding distance. Therefore, the projecting height of the bottom portion rib 213 can be increased by the amount, which corresponds to this distance between the rib connecting part 211 c and the yoke bottom portion 141 a in the fan axial direction.

Furthermore, according to the present embodiment, each primary air flow passage 211 d, which guides the air discharged from the corresponding opening hole 141 c of the yoke bottom portion 141 a toward the outer side in the radial direction of the fan central axis CLf, is formed between the corresponding adjacent two of the bottom portion ribs 213. Therefore, the air, which is outputted from the opening hole 141 c, is smoothly guided to the outer side in the radial direction of the fan central axis CLf. Thereby, the outflow of the air from the inside of the yoke 141 through the opening holes 141 c can be promoted.

Furthermore, according to the present embodiment, the bottom portion ribs 213 are respectively formed such that the flow of the air, which is outputted from the corresponding primary air flow passage 211 d, extends continuously into the corresponding secondary air flow passage 212 b that guides the air from the one end 212 c side to the other end 212 d side of the fan boss tubular portion 212. Therefore, the air, which flows in the primary air flow passage 211 d, is guided to the outside of the fan boss 21 through the corresponding secondary air flow passage 212 b. Thereby, it is possible to promote the outflow of the air from the inside of the yoke 141 through the opening holes 141 c.

Furthermore, according to the present embodiment, each of the tubular portion ribs 214 is tilted relative to the corresponding fan radial direction in the counter-rotational direction that is opposite from the fan rotational direction DRf such that the amount of displacement of the tubular portion rib 214, which is measured from the corresponding fan radial direction of the fan central axis CLf in the counter-rotational direction, is progressively increased toward the radially outer side in the corresponding fan radial direction of the fan central axis CLf. Also, each of the bottom portion ribs 213 is tilted relative to the corresponding fan radial direction in the counter-rotational direction that is opposite from the fan rotational direction DRf such that the amount of displacement of the bottom portion rib 213, which is measured from the corresponding fan radial direction of the fan central axis CLf in the counter-rotational direction, is progressively increased toward the radially outer side in the corresponding fan radial direction of the fan central axis CLf. Therefore, the bottom portion ribs 213 and the tubular portion ribs 214 function as the fan blades of the turbo fan. Thereby, it is possible to promote the outflow of the air from the inside of the yoke 141 through the opening holes 141 c.

Furthermore, according to the present embodiment, the bottom portion ribs 213, which promote the cooling of the electric motor 10, are parts of the fan boss 21. Therefore, it is not required to separately provide a member that promotes the cooling of the electric motor 10. Thereby, it is possible to simplify the structure of the air blower 8.

Second Embodiment

Next, a second embodiment will be described. In the present embodiment, differences, which are different from the first embodiment, will be mainly described, and the discussion of the identical portions or the equivalent portions will be omitted or simplified.

FIG. 7 is a view of the fan boss 21 alone taken in the direction of the arrow IV in FIG. 3 according to the present embodiment, corresponding to FIG. 6 of the first embodiment. In the view taken in the fan axial direction, each of the bottom portion ribs 213 and the tubular portion ribs 214 of the first embodiment is tilted relative the corresponding fan radial direction in the manner similar to that of the fan blades of the turbo fan. In contrast, each of the bottom portion ribs 213 and the tubular portion ribs 214 of the present embodiment is tilted relative the corresponding fan radial direction in a manner similar to that of fan blades of a sirocco fan. Specifically, each of the tubular portion ribs 214 is tilted relative to the corresponding fan radial direction in the fan rotational direction DRf such that the amount of displacement of the tubular portion rib 214, which is measured from the corresponding fan radial direction of the fan central axis CLf in the fan rotational direction DRf, is progressively increased toward the radially outer side in the corresponding fan radial direction of the fan central axis CLf. Also, each of the bottom portion ribs 213 is tilted relative to the corresponding fan radial direction in the fan rotational direction DRf such that the amount of displacement of the bottom portion rib 213, which is measured from the corresponding fan radial direction of the fan central axis CLf in the fan rotational direction DRf, is progressively increased toward the radially outer side in the corresponding fan radial direction of the fan central axis CLf.

The bottom portion ribs 213 and the tubular portion ribs 214 are formed in the above described manner, so that the bottom portion ribs 213 and the tubular portion ribs 214 function as the fan blades of the sirocco fan. Therefore, it is possible to promote the outflow of the air from the inside of the yoke 141 through the opening holes 141 c.

In the present embodiment, the advantages, which are achieved by the structure that is common to the first embodiment described above, can be achieved like in the first embodiment.

Other Embodiments

(1) In each of the above embodiments, the fan 20 includes the insert member 211 a made of the metal, and thereby the fan 20 is made from the resin material and the metal material through the insert molding. However, this is merely one example, and the fan 20 may be formed only from the resin through injection molding, which is other than the insert molding.

(2) In each of the above embodiments, the bottom portion ribs 213 of the fan boss 21 are respectively formed such that the bottom portion rib 213 does not project from the corresponding opening hole 141 c of the yoke bottom portion 141 a toward the stator 15 side in the fan axial direction. However, this is merely one example, and each of the bottom portion ribs 213 may project from the opening hole 141 c toward the stator 15 side within an extent that does not cause an interference of the bottom portion rib 213 with the non-rotatable member, such as the stator 15.

(3) In each of the above embodiments, each of the bottom portion ribs 213 of the fan boss 21 is connected to the corresponding one of the tubular portion ribs 214. However, this is merely one example, and the bottom portion rib 213 may not be connected to the tubular portion rib 214 as long as the air, which is outputted from the primary air flow passage 211 d, can smoothly flow into the secondary air flow passage 212 b.

(4) In each of the above embodiments, the bottom portion ribs 213 project from the fan boss bottom portion 211. Specifically, as shown in FIG. 5, the bottom portion ribs 213 are formed in the outer peripheral resin portion 211 b of the fan boss bottom portion 211. However, this is merely one example, and the bottom portion ribs 213 may not be formed in the insert member 211 a of the fan boss bottom portion 211.

(5) In each of the above embodiments, the fan 20 is the axial fan. However, this is mere one example, and the fan 20 may be another type that is other than the axial type as long as the outer rotor 14 of the electric motor 10 is placed in the inside of the fan boss 21. For example, the fan 20 may be a centrifugal fan or a mixed-flow fan.

The present disclosure should not be limited to the above embodiments. The present disclosure encompasses various modifications and variations within the equivalent scope. In each of the above embodiments, it is clear that the components of the embodiment are not necessarily indispensable unless the components are explicitly stated as indispensable and thought to be theoretically indispensable. When numerals such as the number, values, amounts, and ranges of components of each embodiment are referred to in each above embodiment, the numerals are not limited to the specific ones unless the numerals are explicitly indispensable and clearly thought to be theoretically limited to the specific ones. In each of the above embodiments, when materials, shapes and positional relationships of the components are referred to, the materials, shapes and positional relationships are not limited to the specific ones unless the materials, shapes and positional relationship are explicitly shown and theoretically limited to the specific ones. 

What is claimed is: 1-9. (canceled)
 10. An air blower comprising: a fan that includes: a fan boss, which is shaped into a bottomed tubular form; and a plurality of blades, which are formed at an outer side of the fan boss, wherein the fan is rotatable about a fan central axis; and an electric motor that includes: an outer rotor that is placed in an inside of the fan boss and includes a bottomed rotor member, wherein the bottomed rotor member is shaped into a bottomed tubular form and is rotatable integrally with the fan boss; and a stator that is a non-rotatable member placed in an inside of the bottomed rotor member, wherein: the bottomed rotor member includes a rotor member bottom portion that forms a bottom portion of the bottomed rotor member while an opening hole is formed in the rotor member bottom portion to extend through the rotor member bottom portion in an axial direction of the fan central axis; the fan boss includes: a fan boss bottom portion that is stacked on the rotor member bottom portion in the axial direction and forms a bottom portion of the fan boss; and a bottom portion rib that projects from the fan boss bottom portion toward the rotor member bottom portion side at a corresponding location of the fan boss bottom portion that is overlapped with the opening hole in the axial direction while the bottom portion rib promotes discharge of air from the inside of the bottomed rotor member through the opening hole in response to rotation of the fan; the fan boss bottom portion includes a rib connecting part at a corresponding location of the fan boss bottom portion that is overlapped with the opening hole in the axial direction while a base end of the bottom portion rib is joined to the rib connecting part; and the rib connecting part is spaced from the rotor member bottom portion in the axial direction by a corresponding distance.
 11. The air blower according to claim 10, wherein the bottom portion rib is formed such that at least a portion of the bottom portion rib is inserted into the opening hole.
 12. The air blower according to claim 10, wherein the bottom portion rib is formed such that the bottom portion rib does not project from the opening hole toward the stator side.
 13. An air blower comprising: a fan that includes: a fan boss, which is shaped into a bottomed tubular form; and a plurality of blades, which are formed at an outer side of the fan boss, wherein the fan is rotatable about a fan central axis; and an electric motor that includes: an outer rotor that is placed in an inside of the fan boss and includes a bottomed rotor member, wherein the bottomed rotor member is shaped into a bottomed tubular form and is rotatable integrally with the fan boss; and a stator that is a non-rotatable member placed in an inside of the bottomed rotor member, wherein: the bottomed rotor member includes a rotor member bottom portion that forms a bottom portion of the bottomed rotor member while an opening hole is formed in the rotor member bottom portion to extend through the rotor member bottom portion in an axial direction of the fan central axis; the fan boss includes: a fan boss bottom portion that is stacked on the rotor member bottom portion in the axial direction and forms a bottom portion of the fan boss; and a bottom portion rib that projects from the fan boss bottom portion toward the rotor member bottom portion side at a corresponding location of the fan boss bottom portion that is overlapped with the opening hole in the axial direction while the bottom portion rib promotes discharge of air from the inside of the bottomed rotor member through the opening hole in response to rotation of the fan; the bottom portion rib is one of a plurality of bottom portion ribs that are arranged one after another in a circumferential direction about the fan central axis; and an air flow passage, which guides the air discharged from the opening hole toward an outer side in a radial direction of the fan central axis, is formed between corresponding adjacent two of the plurality of bottom portion ribs.
 14. The air blower according to claim 13, wherein: the fan boss bottom portion includes a rib connecting part at a corresponding location of the fan boss bottom portion that is overlapped with the opening hole in the axial direction while a base end of the bottom portion rib is joined to the rib connecting part; and the rib connecting part is spaced from the rotor member bottom portion in the axial direction by a corresponding distance.
 15. The air blower according to claim 13, wherein: the air flow passage is a primary air flow passage; the fan boss includes: a fan boss tubular portion, which is shaped into a tubular form and is placed on a radially outer side of the bottomed rotor member; and a plurality of tubular portion ribs, which project from the fan boss tubular portion toward an inner side of the fan boss tubular portion; the fan boss tubular portion is joined to the fan boss bottom portion through one end of the fan boss tubular portion; the plurality of tubular portion ribs is arranged one after another in the circumferential direction, and each of a plurality of secondary air flow passages, which guide the air from the one end to another end of the fan boss tubular portion, is formed between corresponding adjacent two of the plurality of bottom portion ribs; and the plurality of bottom portion ribs is formed such that a flow of the air, which is outputted from the primary air flow passage, continuously extends into a corresponding one of the plurality of secondary air flow passages.
 16. The air blower according to claim 13, wherein: the air flow passage is a primary air flow passage; the fan boss includes: a fan boss tubular portion, which is shaped into a tubular form and is placed on a radially outer side of the bottomed rotor member; and a plurality of tubular portion ribs, which project from the fan boss tubular portion toward an inner side of the fan boss tubular portion; the fan boss tubular portion is joined to the fan boss bottom portion through one end of the fan boss tubular portion; the plurality of tubular portion ribs is arranged one after another in the circumferential direction, and each of a plurality of secondary air flow passages, which guide the air from the one end to another end of the fan boss tubular portion, is formed between corresponding adjacent two of the plurality of tubular portion ribs; each of the plurality of bottom portion ribs is connected to a corresponding one of the plurality of tubular portion ribs; and the primary air flow passage is connected in series with a corresponding one of the plurality of secondary air flow passages.
 17. The air blower according to claim 15, wherein: each of the plurality of tubular portion ribs is tilted relative to a corresponding radial direction of the fan central axis in a counter-rotational direction that is opposite from a rotational direction of the fan such that an amount of displacement of the tubular portion rib, which is measured from the corresponding radial direction of the fan central axis in the counter-rotational direction, is progressively increased toward a radially outer side in the corresponding radial direction of the fan central axis; and each of the plurality of bottom portion ribs is tilted relative to the corresponding radial direction of the fan central axis the counter-rotational direction that is opposite from the rotational direction of the fan such that an amount of displacement of the bottom portion rib, which is measured from the corresponding radial direction of the fan central axis in the counter-rotational direction, is progressively increased toward the radially outer side in the corresponding radial direction of the fan central axis.
 18. The air blower according to claim 15, wherein: each of the plurality of tubular portion ribs is tilted relative to a corresponding radial direction of the fan central axis in a rotational direction of the fan such that an amount of displacement of the tubular portion rib, which is measured from the corresponding radial direction of the fan central axis in the rotational direction of the fan, is progressively increased toward a radially outer side in the corresponding radial direction of the fan central axis; and each of the plurality of bottom portion ribs is tilted relative to the corresponding radial direction of the fan central axis in the rotational direction of the fan such that an amount of displacement of the bottom portion rib, which is measured from the corresponding radial direction of the fan central axis in the rotational direction of the fan, is progressively increased toward the radially outer side in the corresponding radial direction of the fan central axis.
 19. The air blower according to claim 13, wherein the bottom portion rib is formed such that at least a portion of the bottom portion rib is inserted into the opening hole.
 20. The air blower according to claim 13, wherein the bottom portion rib is formed such that the bottom portion rib does not project from the opening hole toward the stator side. 